Libsparrow

An image can be canceled out by a projection of its exact
negative. Libsparrow consists of two projectors set up to
compete over a single screen: each tries to cancel the output
of the other and overlay its own images.

Both projections tend to show pictures of sparrows and Lower
Hutt scenery, but they very rarely want to show the same
pictures at the same time. Out of this conflict arise complex
patterns of video feedback, which are sometimes
catastrophically altered by people getting close and blocking
a projector or camera.

Libsparrow was first shown at the Dowse Art Gallery in
July 2010.

Libgstsparrow is the software behind
Libsparrow. It is a Gstreamer plug-in that
performs the necessary calibration, decides what it wants to
show, and negates what it doesn't like. It is free software.

Source code

Examples

Here are some videos the work took of itself being installed
at the Dowse. It wasn't quite finished. These pictures are
of course taken from the work's own camera: this is what each
projections uses to decide what to negate.